The present invention relates to a TiO2 film co-doped with yttrium and erbium and a method for producing the yttrium and erbium co-doped TiO2 film, and more particularly to an yttrium and erbium co-doped TiO2 film used in a planar optical waveguide amplifier.
Owing to the development of network communication, the loading of the network information transference is heavier and heavier. For increasing the data capacity carried by the transform system, the optical fiber system is applied in the communication system for satisfying the demand.
The most important elements of the optical communication system are light source and optical-guided medium. Owing to the disclosure of the semiconductor laser, the long effect and stable light source can be practically applied. At the same time, the quartz optical fiber having low transmission loss has been developed. However, during optical fiber transmission, the transmission loss is inevitable. Thus, it is necessary to set an amplifier at the intermediate station for a long distance transmission. Traditionally, the amplifier is used to transfer an optical signal to an electrical signal, amplify the electrical signal, transfer the amplified electrical signal to the amplified optical signal, and transmit out the amplified optical signal. After the disclosure of the erbium-doped fiber amplifier (EDFA), however, the optical signal can be directly amplified and transmitted out.
During the light transmission, the light source having a wavelength of 1.53 xcexcm has lower loss and is harmless for human eyes. When erbium ion is excited by the laser with the wavelength of 1.48 xcexcm, 0.98 xcexcm or 0.8 xcexcm, the electron located on the first exciting state will jump back to the ground state and irradiate an infrared ray with wavelength of 1.53 xcexcm. The infrared spectra are the light source applied in the current optical fiber communication.
Currently, along the development and upgrade of the IC semiconductor producing technology, the microphoto-electromechanic system is quickly developed. For the integrated optics devices, the planar optical amplifier has very important applications. Furthermore, because the size of the planar optical amplifier is much smaller than that of the erbium-doped fiber amplifier, the erbium-doped planar optical waveguide amplifier becomes an important issue in the integrated optics. Referring to the erbium-doped planar optical waveguide amplifier, most researches are focus on either the process improvement or the different host selection. Generally, the major material of the host is oxide glass, such as pure silica, soda-lime silicate, phosposilicate and aluminosilicate glass, because the oxide glass is the major material for current optical fibers. However, the ceramics material such as Al2O3, TiO2, Y2O3 and LiNbO4, or the amorphous silicon material are also used to be the host. The shape and intensity of erbium-ion fluorescence spectrum are affected by different host. Furthermore, the fluorescence spectral characteristics are dependent on the solubility, or the radiative/non-radiactive relaxation of the erbium ion in the host.
The cross-relaxation between erbium ions will decrease the number of excited erbium ion. The cross-relaxation strength between erbium ions is dependent on the distance between the erbium ions. That is, while the clustering effect of erbium ions increases, the photoluminescence efficiency decreases. In addition, a hydroxide group is a photoluminescence quenching center because the second harmonic vibration of the hydroxide group can produce resonant effect with the photoluminescence at the wavelength about 1.54 xcexcm of erbium ion, which results in the photoluminescence efficiency decreasing. Moreover, the up-conversion phenomenon caused by the cross-relaxation effect between erbium ions will also decrease the photoluminescence efficiency. Therefore, the photoluminescence efficiency can be improved by increasing the erbium ion solubility in host, decreasing the hydroxide group content in host, or decreasing the probability of the up-conversion, and more especially by increasing the erbium ion solubility in host. Generally, the aluminum ion is doped into the silicon oxide structure for increasing the erbium ion solubility because the aluminum ion can be a network former and a network modifier to break the tetrahedron network structure of silicon oxide. Thus, the number of non-bridging oxygen is increased, which further increases the erbium ion solubility.
Another way to increase photoluminescence efficiency is basically to change host materials because the erbium ion solubility in host is strongly host-dependent. Thus, a proper host can increase the erbium ion solubility and further increase the photoluminescence efficiency. Since TiO2 host has higher refraction index (n=2.52 for anatase and n=2.76 for rutile), the optical modes are increased for enhancing transmission efficiency and decreasing the bending radii of the optical waveguide. Hence, the size of optical waveguide device is largely decreased. In addition, TiO2 host also has lower phonon energy ( less than 700 cmxe2x88x921), so the excited electrons are decreased by non-radiative losing rate.
Therefore, Er3+-doped TiO2-based film is applied in the planar optical waveguide amplifier. However, the photoluminescence properties of Er3+-doped TiO2 film applied in the planar optical waveguide amplifier are not as good as expectation.
Therefore, the purpose of the present invention is to develop a material and a method to deal with the above situations encountered in the prior art.
It is therefore an object of the present invention to propose an erbium and yttrium co-doped TiO2 material and a method for producing the erbium and yttrium co-doped TiO2 film used in a planar optical waveguide amplifier for increasing photoluminescence at the wavelength about 1.54 xcexcm in emissive intensity.
It is therefore another object of the present invention to propose an erbium and yttrium co-doped TiO2 material and a method for producing the erbium and yttrium co-doped TiO2 film used in a planar optical waveguide amplifier for increasing photoluminescence at the wavelength about 1.54 xcexcm in bandwidth.
It is therefore an additional object of the present invention to propose an erbium and yttrium co-doped TiO2 material and a method for producing the erbium and yttrium co-doped TiO2 film used in a planar optical waveguide amplifier for decreasing light scattering.
It is therefore an additional object of the present invention to propose an erbium and yttrium co-doped TiO2 material and a method for producing the erbium and yttrium co-doped TiO2 film used in a planar optical waveguide amplifier for decreasing processing temperature and further reducing the producing cost.
According to one aspect of the present invention, there is provided a doped TiO2 material for forming a film used in a planar optical waveguide amplifier. The doped TiO2 material includes 100 mol % TiO2 precursor compound, about 0.1-10 mol % erbium ion (Er3+) precursor compound, and about 1-50 mol % yttrium ion (Y3+) precursor compound, thereby forming the doped TiO2 film co-doped with erbium and yttrium as an amorphous structure to achieve the enhancing effect on photoluminescence properties.
Preferably, the erbium ion (Er3+) precursor compound is selected from a group consisting of erbium acetate, erbium carbonate, erbium chloride, erbium oxalate, erbium nitrate, and erbium isopropoxide.
Preferably, the TiO2 precursor compound is selected from a group consisting of titanium isopropoxide, titanium ethoxide, titanium chloride, and titanium butoxide.
Preferably, the yttrium ion (Y3+) precursor compound is selected from a group consisting of yttrium acetate, yttrium carbonate, yttrium chloride, yttrium oxalate, yttrium nitrate, and yttrium isopropoxide.
According to another aspect of the present invention, there is provided a method for forming a doped TiO2 film used in a planar optical waveguide amplifier. The method includes steps of (a) preparing a titanium solution having 100 mol % titanium ion (Ti4+) precursor compound, (b) preparing a yttrium solution having the concentration about 1-50 mol % yttrium ion (Er3+) precursor compound, (c) adding the yttrium solution and an erbium powder with the concentration about 0.1-20 mol % into the titanium solution for forming a sol-gel solution and (d) forming the TiO2 film co-doped with Er3+ and Y3+ by spin-coating and thermal treatment.
Certainly, the step (a) can further include steps of (a1) dissolving titanium isopropoxide in acetic acid to from a first solution and (a2) adding 2-methoxyethanol into the first solution.
Certainly, the step (b) can further include step of dissolving yttrium acetate in a mixed solution of methanol and ethylene glycol.
Preferably, the step (d) further includes steps of (d1) spin-coating the sol-gel solution on a substrate, (d2) thermal treating the substrate at a first specific temperature for evaporating organic materials thereof, (d3) repeating steps of spin-coating and thermal treating until the film reaching a specific thickness and (d4) thermal treating the film of the substrate at a second specific temperature for forming the TiO2 film co-doped with Er3+ and Y3+.
Certainly, the substrate can be made of a material selected from a group consisting quartz, glass, and silica oxide on silicon (SOS).
Preferably, the first specific temperature is about 400xc2x0 C. and the second specific temperature is ranged from 500 to 900xc2x0 C.
Preferably, the specific thickness of the film is ranged from 0.1 to 2 xcexcm.
The present invention may best be understood through the following description with reference to the accompanying drawings, in which: